/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.db.mpp.aggregation.timerangeiterator;

import org.apache.iotdb.tsfile.read.common.TimeRange;

/**
 * Used for aggregation with only one time window. i.e. Aggregation without group by.
 */
public class SingleTimeWindowIterator implements ITimeRangeIterator {

    // total query [startTime, endTime)
    private final long startTime;
    private final long endTime;

    private TimeRange curTimeRange;
    private boolean hasCachedTimeRange;

    public SingleTimeWindowIterator(long startTime, long endTime) {
        this.startTime = startTime;
        this.endTime = endTime;
    }

    @Override
    public TimeRange getFirstTimeRange() {
        return new TimeRange(startTime, endTime);
    }

    @Override
    public boolean hasNextTimeRange() {
        if (hasCachedTimeRange) {
            return true;
        }
        if (curTimeRange == null) {
            curTimeRange = getFirstTimeRange();
            hasCachedTimeRange = true;
        }
        return hasCachedTimeRange;
    }

    @Override
    public TimeRange nextTimeRange() {
        if (hasCachedTimeRange || hasNextTimeRange()) {
            hasCachedTimeRange = false;
            return curTimeRange;
        }
        return null;
    }

    @Override
    public boolean isAscending() {
        return false;
    }

    @Override
    public long currentOutputTime() {
        return curTimeRange.getMin();
    }

    @Override
    public long getTotalIntervalNum() {
        return 1;
    }
}
